The M Performance nomenclature was introduced a few years ago and is gradually being transitioned to the entire BMW lineup as models are redesigned or updated. For instance, the next generation 3 Series and 4 Series will adopt the M340i and M440i names respectively for their top-of-the-line models. And, in a year or so, the X5 50i and X6 50i will get the update to M50i when they adopt the new 530hp motor from the new M850i.